Stoves and furnaces – Stoves – Heating
Reexamination Certificate
1999-04-29
2001-05-22
Lazarus, Ira S. (Department: 3743)
Stoves and furnaces
Stoves
Heating
C454S044000, C138S122000, C138S113000, C138S114000, C126S30700R
Reexamination Certificate
active
06234163
ABSTRACT:
The present invention is concerned with atmospheric boilers and more particularly with a novel form of ducting for use with such boilers.
While conventional atmospheric boilers require only a unitary or single-layer ducting system to convey discharge gases to the atmosphere, double-walled ducting may be adopted in some situations. For example, by encircling the discharge duct with a concentric outer wall, it is possible to form an annular space by means of which the gas being discharged is insulated from the surroundings by air in that space, thereby maintaining the temperature of the gas until it is eventually discharged from the flue. In this way, undesirable condensation into the flue of liquid from the gas is minimised or prevented.
Although it is possible to construct a double-walled duct by installing independent lengths of unitary ducting concentrically at the site of intended use, it is potentially easier to make use of double-walled ducting for this purpose. However, such ducting is usually required to follow a non-linear path from the boiler to the eventual discharge point and therefore specific components, for example elbow bends and other connectors, are needed for this purpose. Double-walled ducting with flexible inner walls has been devised but is not much favoured as there is a serious possibility of the inner wall sagging in horizontal ducting runs.
It is an object of the present invention to provide a novel form of flue ducting for atmospheric boilers, by means of which at least some of the disadvantages of conventional such ducting are overcome and/or positive advantages are conveyed.
The flue ducting according to the present invention comprises two coaxial generally tubular ducts, a generally undulating linear spacer between said ducts, and linear features on the mutually facing surfaces of said ducts, said features being shaped to engage said undulating spacer, one end of the annular space between the ducts being closed.
It is an important beneficial feature of the flue ducting according to the present invention that the undulating linear spacer maintains the mutual spacing-apart of the two coaxial ducts, thereby preserving the integrity of the annular space between the ducts even when the ducts are bent into a nonlinear configuration. Thus the ducting for an associated atmospheric boiler may be modified to adapt to a required non-linearity of the ducting without the provision of pre-formed duct bends or other junction pieces.
In order to enable the two coaxial ducts to be shaped to form bends between the ends of the flue ducting, the outer and/or the inner flue duct may be constructed of a material which can be bent without harm to its integrity. For example, the duct may be of a material which has inherent flexibility or, more preferably, the duct may be of a material which is of low inherent flexibility, for example of a metal such as steel or aluminium, but formed in a construction by which a degree of overall flexibility is imparted. By way of example, each or either duct may be formed of a strip material wound helically to give a generally tubular duct of some flexibility.
Additional flexibility, for example of the inner duct in particular, may be afforded by forming the duct from two or more superimposed layers of reduced thickness. For example, the inner duct may comprise two thicknesses of aluminium, each 0.006 inches thick.
Each of the two coaxial ducts has, in its surface facing the other duct, a linear feature designed to engage an undulating spacer. By way of example, that feature may be a continuous or discontinuous spiral groove formed on or in the duct surface, for example during the constructing of the relevant duct. The generally undulating linear spacer between the ducts may be of undulating spiral form, for example a continuous coil with undulations superimposed on the coils of the spiral. Most preferably, the spacer is made of a resilient material, for example in the overall form of a coiled spring.
When one or both of the coaxial ducts is formed of a material and/or in a construction by means of which it/their overall length and/or diameter may be varied, it is possible thereby to modify the radial dimension of the annular space between the ducts. By this means, the size of this space may be reduced to, say, one inch or less, and in particular to preferred values of the order of one half or one quarter of an inch.
One end of the annular space between the ducts is closed in use. When the ducting has been installed to convey to atmosphere the flue gases from an atmospheric boiler, that end of the annular cavity which is uppermost and nearer to the discharge terminal is the closed end. The cavity may be closed by a sealing ring, the other end of the annular cavity, nearer to the boiler, being left open to admit access of ambient air to the cavity. The air thus admitted to the cavity and retained therein effectively insulates boiler waste gas within the innermost duct from the potentially cooling effect of the ambient atmosphere and assists in maintaining the temperature of the waste gas above its dew point.
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Bliss McGlynn P.C.
Lazarus Ira S.
Lee David
LandOfFree
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